U.S. Pat. No. 4,629,676 (Hayakawa et al) and European Patent No. 0174634 (Fuji Photo Film Co., Ltd.) disclose an image forming process comprising the steps of imagewise exposing to light a light-sensitive material and heating the light-sensitive material. The light-sensitive material comprises a support and a light-sensitive hardening layer containing silver halide, a reducing agent and an ethylenically unsaturated polymerizable compound. The silver halide is developed by heating the light-sensitive material to form a polymer image. The polymerization is initiated by an oxidation radical of the reducing agent (including a radical formed from an oxidation product of the reducing agent).
The image forming process can be applied for the preparation of a lithographic plate.
U.S. Pat. No. 5,122,443 (Takeda), U.S. Pat. No. 5,290,659 (Takeda) and European Patent No. 0426192 (Fuji Photo Film Co., Ltd.) disclose embodiments of the light-sensitive materials, which are advantageously used for the preparation of a lithographic plate. The light-sensitive material for the lithographic plate generally comprises a hardening layer and a light-sensitive layer provided on a support. The hardening layer contains an ethylenically unsaturated polymerizable compound. The light-sensitive layer contains silver halide. The hardening layer or the light-sensitive layer further contains a reducing agent.
The process for the preparation of a lithographic plate comprises the steps of imagewise exposing to light the light-sensitive material, heating the material to harden the polymerizable compound, removing the light-sensitive layer from the material, and removing the unhardened area of the hardening layer with an etching solution. The formed replica image is used as a printing plate. In the process, an acrylic or methacrylic ester of a polyhydric alcohol (e.g., pentaerythritol) has usually been used as the ethylenically unsaturated polymerizable compound.